Ferrite thin film, method of manufacturing the same and electromagnetic noise suppressor using the same

ABSTRACT

A ferrite film is formed by regularly arranging constituents such as magnetized grains or one analogous to that. In the ferrite film, the constituents have at least one of the uniaxial anisotropy and the multiaxial anisotropy. The ferrite film has the magnetic anisotropy or the magnetic isotropy. The ferrite film is formed by the use of the plating method in the presence of a magnetic field. Furthermore, an electromagnetic noise suppressor includes the ferrite film.

This is a Divisional application of application Ser. No. 10/660,071filed Sep. 11, 2003, now U.S. Pat.No. 7,160,636.

The present application claims priority to prior Japanese patentapplications JP 2002-268932, JP-2002-26867 and JP 2002-269009, thedisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a spinel type ferrite film high in theutility value in particular in high frequency magnetic devices such as,inductance elements, impedance elements, magnetic heads, microwaveelements, magnetostrictive elements and electromagnetic interferencesuppressors that are used to suppress electromagnetic interference owingto the unnecessary electromagnetic waves in a high frequency region anda manufacturing method thereof.

In a ferrite plating process, as mentioned in Japanese Unexamined PatentPublication No. S59-111929 (hereinafter referred to as “literature 1”),an aqueous solution containing at least ferrous ion as a metal ion isbrought into contact with a solid surface, thereby Fe²⁺ alone or both ofFe²⁺ and another metal ion are allowed to be absorbed on the solidsurface, subsequently the absorbed Fe²⁺ is oxidized and thereby Fe³⁺ isobtained, this causes a ferrite crystallization reaction with the metalion in the aqueous solution, and thereby a ferrite film is formed on thesolid surface.

So far, there are various processes that are proposed based on the aboveprocess: one that intends to homogenize a ferrite film and improve areaction rate (for instance, Japanese Unexamined Patent Publication No.S60-140713 (hereinafter referred to as “literature 2”)), another onethat intends to form a ferrite film on various solids by endowing asolid surface with the surface activity (for instance, JP-A No.61-030674(hereinafter referred to as “literature 3”)), and still another one thatintends to improve the formation rate of a ferrite film (for instance,Japanese Unexamined Patent Publications Nos. S61-179877 and S63-42378,and JP-A No.02-116631 (hereinafter referred to, respectively, as“literature 4”, “literature 5” and “literature 6”)).

In the ferrite plating, as far as a solid on which a ferrite film isintended to form is resistant against the aqueous solution, any solidcan be used. Furthermore, since it is a reaction through an aqueoussolution, an advantage is made in that a spinel type ferrite film can beformed at a relatively low temperature between room temperature and aboiling point or less of the aqueous solution. Accordingly, incomparison with other processes of forming a ferrite film, a limitingrange on the solid is smaller.

In order to improve the characteristics of such ferrite films, varioustrials have been attempted.

For instance, Japanese Unexamined Patent Publication No. H02-116624(hereinafter referred to as “literature 7”) discloses a method in whichwith paying attention to an improvement in the magnetic characteristicsof a ferrite film, the ferrite plating is carried out in a magneticfield, and thereby the soft magnetic characteristics are improved.

Furthermore, JP-A No.3-38006 (hereinafter referred to as “literature 8”)proposes a method in which a solution containing at least ferrous ion isbrought into contact with a substrate in a magnetic field, the ferriteplating is applied on a solid surface in a magnetic field, and thereby aferrite film having the uniaxial anisotropy is obtained; and a method inwhich an oxidant is contained in a solution to oxidize ferrous ion.

Still furthermore, JP-A No.60-202522 (hereinafter referred to as“literature 9”) discloses that when attentions are paid to a compositionof ferrite and a weight ratio of Co/Fe in a film is set in the range offrom 0.001 to 0.3, excellent magnetic characteristics can be obtained.

According to the literature 6, it is proposed to repeat a step in whichafter a reaction solution containing at least ferrous ion is broughtinto contact with a substrate, a solution containing at least an oxidantis brought into contact with the substrate, and thereby to form aferrite film on a surface of the substrate; and it is said that therebya formation rate of the ferrite film can be improved.

However, in the literature 6, no clear mention is made of a step ofremoving the reaction solution containing at least ferrous ion and thesolution containing at least the oxidant.

Furthermore, a method is proposed in which a ferrite film is formed on asubstrate having the center line average roughness Ra of 0.01 μm or more(for instance, JP-A No.1-246149 (hereinafter referred to as “literature10”)).

In the case of the literature 10, in an embodiment thereof, it isdisclosed that when a ferrite film is formed on a substrate having thecenter line average roughness Ra in the range of from 0.01 to 0.8 μm, ahomogeneous film free from irregularity in a thickness can be obtained.

However, the ferrite films according to the above-mentioned existingprocesses, in view of applying to an inductance element, impedanceelement, magnetic head, microwave element, magnetostrictive element andelectromagnetic interference suppressor in a high frequency region, areinsufficient in the soft magnetic characteristics. Accordingly, a largeproblem existed as to applications or adaptations to various kinds ofelectronic components and so on. In order to overcome the problems,specifically, imparting a film a magnetic uniaxial anisotropy,optimizing a chemical composition of the film, and homogenizing the filmbecome important points.

A film that is manufactured according to a general ferrite platingprocess (for instance, literature 1) does not have the magneticdirectivity (isotropic); accordingly, when a constituent element of aferrite film has the uniaxial anisotropy and the magnetic permeabilitythereof is assumed to be A, the magnetic permeability of as a whole filmbecomes about A/2 and excellent potential in the soft magneticcharacteristics that the ferrite film intrinsically has cannot beextracted. Furthermore, in the case of a ferrite film that has theuniaxial anisotropy such as disclosed in the literature 8 being used inan inductance element, when for instance a spiral coil is used, aproblem exists in that owing to the anisotropy of the magnetic film aportion where the magnetic flux density is locally lowered is generatedinside of the element, as a result an inductance as a whole is lowered.

Furthermore, as mentioned above, various improvements have been proposedto improve a formation rate of a ferrite film; however, from anindustrial productivity point of view, these are insufficient;accordingly, a large problem has been remained in the applications tovarious kinds of electronic components or in the adaptability thereto.

Still furthermore, in the above literatures 7 and 8 that pay attentionto an improvement in the magnetic characteristics, in an embodiment thatis a specific explanation thereof, there is a description that “aplating solution can be separately supplied”; however, all embodimentsin, for instance, the literature 8 adopt a method in which a pluralityof plating solutions is mixed before the ferrite crystallization andsupplied to a substrate. Accordingly, it is supposed that because fineferrite grains that are secondarily formed other than on a solid surfacedisturb the crystal growth or Fe²⁺ is unevenly absorbed on a solidsurface, a ferrite film that is an aggregation of homogeneous grains isobtained with difficulty.

Furthermore, the literature 9, though paying attentions to relationshipbetween compositions and the magnetic characteristics, aims usage asmagnetic recording media, intends to realize higher coercive force andhigher residual magnetic flux density, but does not relate to a ferritefilm that is used in an inductance element, impedance element, magnetichead, microwave element, magnetostrictive element and high frequencymagnetic device; that is, the literature 9 is a technique that relatesto one that is obviously different in the characteristics required forhigh frequency magnetic devices such as an electromagnetic interferencesuppressor that is used to suppress electromagnetic interference owingto unnecessary electromagnetic waves in the high frequency region.

On the other hand, in the case of the technique by which a ferrite filmis formed on the above-mentioned substrate, in view of applications torecent magnetic devices, a magnetic substance that is used therefor, inthe magnetic characteristics thereof, is necessary to be highspecifically in the magnetic permeability. In order that a film that isobtained by the ferrite plating process may have high magneticpermeability, control of a composition of a film, in particular controlof crystal orientation of grains that form the film is indispensable.

However, according to the above-mentioned existing processes, in all ofthe processes, a technique for controlling the crystal orientation thattakes correlation with the magnetic characteristics into considerationis not introduced (that is, for instance, in the literature 10, nomention is made of correlation between the center line average roughnessRa of the substrate and the crystal orientation and the magneticcharacteristics of the film; in the literature 3, there is describedthat in order to supply a homogeneous film excellent in theadhesiveness, a surface of the substrate is necessary to be plasmatreated; furthermore, in the literature 7, the magnetic characteristicsof a film that is obtained are taken into consideration, however nomention is made of steps of removing the reaction solution and theoxidizing solution and the correlation between the crystal structure andthe magnetic characteristics of the film of the substrate and thesurface roughness of the substrate); as a result, a problem exists inthat high magnetic permeability cannot be obtained.

In the case of the ferrite film particularly due to the ferrite platingprocess, as mentioned above, the ferrite film is formed through crystalgrowth from a starting point on the surface of the substrate; however,according to the existing processes, since fine ferrite grainssecondarily formed other than on the surface of the substrate disturbthe crystal growth or Fe²⁺ is unevenly absorbed on the surface of thesubstrate, the crystal orientation can be controlled with difficulty(for instance, as in the literature 10, when a ferrite film is formed ona surface of a substrate that is extremely small in the center lineaverage roughness Ra, a homogeneous film can be obtained withdifficulty, and the crystal orientation can be controlled withdifficulty). As a result, in spite of various improvements so far beingproposed to improve the formation rate of the film, these improvementsare insufficient from a viewpoint of the industrial productivity. Inaddition to the above problem, there is a large technical problem inthat when applying to the magnetic devices and adapting to various kindsof electronic components, high magnetic permeability cannot be obtained.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide, in ferritefilms that are formed according to the ferrite plating process, with aformation rate improved and thereby industrial productivity increased,an extremely homogeneous ferrite film that has the uniaxial anisotropyand large magnetic permeability.

Furthermore, it is a second object of the present invention to provide,in ferrite films that are formed according to the ferrite platingprocess, with a formation rate improved and thereby industrialproductivity increased, an extremely homogeneous ferrite film that doesnot have the magnetic directivity (isotropic).

Still furthermore, it is a third object of the present invention toprovide a method of manufacturing the ferrite film.

Furthermore, it is a fourth object of the present invention to providean electromagnetic noise suppressor in which the ferrite film is used.

Still furthermore, it is a fifth object of the present invention toprovide a method of manufacturing the electromagnetic noise suppressor.

Furthermore, it is a sixth object of the invention to provide ahomogeneous ferrite film that is controlled in the crystal orientationand high in the magnetic permeability, and a method of manufacturing theferrite films according to the ferrite plating process with a formationrate improved and thereby industrial productivity increased.

According to one aspect of the present invention, there is provided aferrite film in which magnetized grains or constituent elementsanalogous to that are regularly arranged.

Here, in the aspect of the present invention, the magnetic anisotropy orthe magnetic isotropy is preferably possessed.

Furthermore, in the aspect of the present invention, the constituentelement having the uniaxial anisotropy preferably includes Co.

Still furthermore, in the aspect of the present invention, theconstituent element having the multiaxial anisotropy preferably includesNi, Zn, Fe and O.

Furthermore, according to another aspect of the present invention, thereis provided a ferrite film in which an intensity ratio of peakscorresponding to a (222) crystal lattice plane and a (311) crystallattice plane in an X-ray diffraction pattern of a film surface,I₂₂₂/I₃₁₁. The intensity ratio is larger than 0.05.

Here, in the aspect of the present invention, at least one kind of Ni,Zn, Fe and O is preferably included.

Furthermore, according to still another aspect of the present invention,there is provided an electromagnetic noise suppressor provided with aferrite film in which magnetized grains or constituent elementsanalogous to that are regularly arranged.

Here, in the above aspect of the present invention, the ferrite film ispreferably formed directly or indirectly on a substrate of any one of asupport, electronic wiring board and semiconductor integrated wafer, andfurthermore, in the ferrite film, magnetized grains or constituentelements analogous to that are preferably regularly arranged.

According to yet another aspect of the present invention, there isprovided a method of manufacturing a ferrite film in which magnetizedgrains or constituent elements analogous to that are regularly arranged.In the method of manufacturing the ferrite film, the ferrite film isformed in the presence of a magnetic field.

According to a further aspect of the present invention, there isprovided a ferrite film which is formed in the presence of a revolvingmagnetic field.

Furthermore, according to a still further aspect of the presentinvention, there is provided a method of manufacturing a ferrite film inwhich magnetized grains or constituent elements analogous to that areregularly arranged. The method of manufacturing a ferrite thin filmincludes the steps of bringing a reaction solution containing at leastferrous ion into contact with a substrate, removing the reactionsolution from the substrate, bringing an oxidizing solution containingat least an oxidant into contact with the substrate, and removing aresidue that does not contribute to the formation of the ferrite film ofthe reaction solution and the oxidizing solution can be obtained.

Still furthermore, according to a yet further aspect of the presentinvention, there is provided a method of suppressing electromagneticnoise that uses an electromagnetic noise suppressor that is providedwith a ferrite film having the magnetic anisotropy. In the aspect of thepresent invention, the ferrite film is disposed with an axis of easymagnetization in substantially parallel with a forwarding direction of ahigh frequency current or conducted noise that is a target of theelectromagnetic noise suppression. Here, in the above aspect of thepresent invention, the ferrite film preferably has magnetized grains orconstituent elements analogous to that that are regularly arranged, andthe constituent elements preferably have the uniaxial anisotropy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram showing columnar grains of a ferrite filminvolving the present invention;

FIG. 1B is a schematic diagram showing particulate grains of a ferritefilm involving the invention;

FIG. 1C is a schematic diagram showing layering grains of a ferrite filminvolving the invention;

FIG. 2 is a schematic front view of an example of plating apparatus thatwas used in a first embodiment according to the invention;

FIG. 3 is a layout diagram when the apparatus in FIG. 2 is seen from adirection vertical to a substrate;

FIG. 4 is a schematic diagram of another example of plating apparatusaccording to the first embodiment of the invention;

FIG. 5 is a layout diagram when the apparatus in FIG. 4 is seen from adirection vertical to a substrate;

FIG. 6 is a schematic diagram of an evaluation system of anelectromagnetic noise suppression effect of a ferrite thin film that wasobtained according to the first embodiment of the invention;

FIG. 7A is a diagram showing an evaluation example of an electromagneticnoise suppression effect of the ferrite thin film that was obtainedaccording to the first embodiment of the invention and showingreflection characteristics (S11);

FIG. 7B is a diagram showing an evaluation example of an electromagneticnoise suppression effect of the ferrite thin film that was obtainedaccording to the first embodiment of the invention and showingtransmission characteristics (ΔS21);

FIG. 8 is aside view showing a basic configuration of ferrite filmformation apparatus according to a second embodiment of the invention;

FIG. 9 is a schematic front view of an example of apparatus according toa third embodiment of the invention;

FIG. 10 is a layout diagram when the apparatus of FIG. 9 was seen from adirection vertical to the substrate;

FIG. 11 is a schematic diagram of another example of apparatus accordingto the third embodiment of the invention; and

FIGS. 12A and 12B are diagrams showing an evaluation example of anelectromagnetic noise suppression effect of a ferrite thin filmaccording to the third embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

First, the present invention will be detailed.

As shown in FIG. 1A, in a ferrite film 19 a formed on a substrate 15,columnar grains 17 a constituting the film 19 a or constituting elementsanalogous to that are very uniformly distributed in the film 19 a.Furthermore, in FIG. 1B, in a ferrite thin film 19 b formed on thesubstrate 15, particulate grains 17 b constituting the film 19 b orconstituting elements analogous to that are very uniformly distributedin the film 19 b. Still furthermore, in FIG. 1C, in a ferrite thin film19 c formed on the substrate 15, layering grains 17 c constituting thefilm 19 c or constituting elements analogous to that are very uniformlydistributed in the film 19 c.

According to the invention, a ferrite thin film in which constituents(grains or constituents analogous to that) constituting a ferrite filmare regularly arranged is obtained; anisotropic directions of theconstituents having the uniaxial anisotropy are aligned in a particulardirection; and thereby an extremely homogeneous ferrite thin film havingthe uniaxial anisotropy in substantially parallel with a thicknessdirection of a thin film as a whole film or in substantially parallelwith an in-plane direction of a thin film can be obtained. Furthermore,when the ferrite thin film, in addition to Ni, Zn, Fe and O, furthercontains Co, the soft magnetic characteristics can be improved.

Here, an amount of Co that is contained in the ferrite film involvingthe invention, by molar ratio, a value of Co/(Fe+Ni+Zn+Co), is 0/3 ormore and 0.3/3 or less, and most preferably in the range ofsubstantially from 0.01/3 to 0.1/3.

Furthermore, in the invention, in a thin film in which an axis of easymagnetization of an obtained film as a whole is in substantiallyparallel with a thickness direction of a ferrite thin film, all in-planedirections of the film become an axis of hard magnetization.Accordingly, excellent potential in the soft magnetic characteristicsintrinsic to the film can be fully extracted, and furthermore highmagnetic permeability that has the same value in all directions in afilm plane can be obtained.

Still furthermore, in a thin film in which an axis of easy magnetizationof an obtained film as a whole is in substantially parallel with anin-plane direction of a ferrite thin film, in a direction perpendicularto the axis of easy magnetization, excellent potential in the softmagnetic characteristics intrinsic to the film can be fully extractedand high magnetic permeability can be obtained.

Specifically, in the invention, when a method of manufacturing a ferritefilm includes a step of bringing a reaction solution containing at leastferrous ion into contact with a substrate; a step of bringing anoxidizing solution containing at least an oxidant into contact with thesubstrate; a step of removing a residue that does not contribute to theformation of the ferrite film of the reaction solution and the oxidizingsolution from the substrate; and furthermore a step of bringing areaction solution and an oxidizing solution into contact with a surfaceof the substrate in a magnetic field, an extremely homogeneous ferritethin film having the uniaxial anisotropy can be obtained with aformation rate improved and thereby industrial productivity increasedand with the constituents (grains) constituting the film arrangedregularly.

Reasons for the ferrite film according to the invention being obtainedare considered as follows.

The ferrite film according to the ferrite plating process, as mentionedabove, is formed through the crystal growth from a starting point on asolid surface. At this time, the ferrite film is a ferrite thin film inwhich constituents (grains or ones analogous to that) having theuniaxial anisotropy are regularly arranged. Accordingly, the reasons forthe existing process described in the. literature 1 giving birth to theisotropic film alone are considered to be in that crystal orientationsimparting the constituents with the uniaxial anisotropy are random.According to the invention, by bringing, for instance, a reactionsolution and an oxidizing solution into contact with a surface of asubstrate in the presence of a magnetic field, directions of anisotropyof the constituents individually having the uniaxial anisotropy are(induced) aligned in a particular direction or uniaxial anisotropy isinduced resulting from a peculiar distribution of Co ions, resulting inobtaining a film having the uniaxial anisotropy as a whole film.

Details of the reasons for the step of removing the reaction solutionand the oxidizing solution improving the formation rate of the ferriteplating film and realizing homogeneous columnar grains are notclarified.

However, it is considered that the step of removing the reactionsolution and the oxidizing solution suppress ferrite fine particles frombeing secondarily formed other than on the surface of the solid andallow Fe²⁺ being uniformly absorbed on the solid surface.

Furthermore, as mentioned above, the literature 7 discloses a method ofapplying the ferrite plating in a magnetic field and thereby improvingthe soft magnetic characteristics, and the literature 8 discloses thatthe ferrite plating in the presence of a magnetic field gives birth to afilm having the uniaxial anisotropy.

However, although there is such a description as that “plating solutionscan be separately supplied” in embodiments, all embodiments adopt amethod in which a plurality of plating solutions is mixed before theferrite crystallization and supplied to a substrate. Accordingly, it issupposed that since fine ferrite particles secondarily formed other thanon the solid surface disturb the crystal growth and Fe²⁺ is unevenlyabsorbed on the solid surface, a ferrite film that is an aggregation ofhomogeneous grains can be obtained with difficulty.

Furthermore, as mentioned above, according to the literature 9, when aweight ratio of Co/Fe in the film is in the range of from 0.001 to 0.3,excellent magnetic characteristics can be obtained. However, theliterature 9 is for use in magnetic recording medium and intends torealize higher coercive force and higher residual magnetic flux density.Accordingly, the usage and directionality are clearly different fromthat of the present invention.

Still furthermore, according to the literature 6, it is proposed that astep in which, after a reaction solution containing at least ferrous ionis brought into contact with a substrate, in the next place a solutioncontaining at least an oxidant is brought into contact with thesubstrate is repeated, and thereby a ferrite film is formed on a surfaceof the substrate. According to the literature 6, thereby, a formationrate of the ferrite film can be improved.

However, in the literature 6, no clear description is made of a step ofremoving the reaction solution containing at least ferrous ion and thesolution containing at least an oxidant.

According to the study of the present inventors, the step of removingthe reaction solution containing at least ferrous ion and the solutioncontaining at least an oxidant is very important and indispensable toimprove the formation rate of the ferrite plating film and to formhomogeneous grains.

Furthermore, because the ferrite plating film according to the inventionhas excellent magnetic loss characteristics in a high frequency region,the ferrite plating film can be used as an electromagnetic noisesuppressor when formed singly or on a support. Furthermore, when theferrite plating film is formed directly at least on one surface of anelectronic wiring board or a semiconductor integrated wafer, anelectronic wiring board or a semiconductor integrated wafer that canconcurrently work as an electromagnetic noise suppressor can berealized. Still furthermore, when the ferrite film that constitutes anelectromagnetic noise suppressor arranges an axis of easy magnetizationin substantially parallel with a forwarding direction of a highfrequency current (conducted noise) that is a target of theelectromagnetic noise suppression, it can realize a method of moreeffectively suppressing the electromagnetic noise.

In the next place, a first embodiment of the invention will bespecifically explained.

With reference to FIGS. 2 and 3, on rotary table 23, substrates 25thereon a ferrite film is formed are disposed sandwiched by magnets 27.The magnets 27 are disposed to apply a magnetic field to the substrates25. Above the substrates 25, nozzles 29 and 31 for spraying a platingliquid to the substrates 25 are disposed, respectively, and the nozzle29 and 31 are communicated with tanks for reserving the respectiveplating liquids. In order to efficiently removing the reaction solutionand the oxidizing solution in the plating step, necessary solutions maybe well prepared by dividing into several portions.

In an example shown in FIG. 2, a case where a solution necessary for theplating is divided into two is shown. Solutions reserved in tanks 33 and35 are supplied through the nozzles 29 and 31, respectively, to thesubstrates 25. At that time, after the solution is supplied through, forinstance, the nozzle 29 to the substrate 25, the supplied solution isremoved by a centrifugal force due to rotation, the solution suppliedthrough the nozzle 31 to the substrate 25 is removed by the centrifugalforce due to rotation, and these steps are repeated.

Also in FIGS. 4 and 5, a case where in plating apparatus 37, when thereaction solution and the oxidizing solution are removed from thesubstrates, the fluidity imparted to the reaction solution and theoxidizing solution owing to gravity is utilized is shown.

Also in FIGS. 4 and 5, similarly to that described in FIGS. 2 and 3, thesolutions reserved in the tanks 33 and 35 are supplied through thenozzles 29 and 31, respectively, to the substrates 25 disposed on atilting table 39. At that time, after the solution is supplied through,for instance, the nozzle 29 to the substrate 25, the supplied solutionis removed owing to the fluidity imparted to the solution by thegravity, after the solution is supplied through the nozzle 31 to thesubstrate 25, the supplied solution is removed owing to the fluidityimparted to the solution by the gravity, and these steps are repeated.

At that time, the magnets 27 apply a magnetic field to the substrates25.

In the present embodiment, a magnetic field is applied in parallel witha direction in which the solution is removed; however, a magnetic fieldis applied which may be in any direction irrespective of a direction inwhich the solution is removed.

Furthermore, in the present invention, an example in which a step inwhich one solution is supplied followed by removing the suppliedsolution and the other solution is supplied followed by removing thesupplied solution is repeated is shown; however, two solutions may besimultaneously supplied.

Next, examples of manufacturing ferrite films according to the inventionwill be specifically explained.

EXAMPLE 1

With reference to FIGS. 2 and 3, on the rotary table 23, as thesubstrate 25, glass plates rendered hydrophilic by plasma treatment aredisposed and heated to 90 degree centigrade under a rotation at 150 rpmand supply of deoxygenated ion exchange water. At that time, it wasconfirmed that on a surface of the substrate 25, a magnetic field ofsubstantially 50 Oe is applied in substantially parallel with a filmplane. In the next place, in the apparatus, N₂ gas was introduced and adeoxygenated atmosphere is established. Two kinds of reaction solutionswere prepared. Into deoxygenated ion exchange water, FeCl₂.4H₂O, NiCl₂.6H₂O, ZnCl₂, and CoCl₂. 6H₂O, respectively, were dissolved by 3.3, 1.3,0.03, and 0.1 g/L, and thereby a solution A was prepared. Intodeoxygenated ion exchange water, FeCl₂.4H₂O, NiCl₂.6H₂O, and ZnCl₂,respectively, were dissolved by 3.3, 1.3, and 0.03 g/L, and thereby asolution B was prepared. One of the reaction solutions A and B and anoxidizing solution that was prepared by dissolving NaNO₂ and CH₃COONH₄,respectively, in deoxygenated ion exchange water by 0.3 and 5.0 g/L weresupplied from the nozzles at a flow rate of 30 ml/min for substantially30 minutes. Thereafter, it was confirmed that on a taken out glasssubstrate, in all cases where the reaction solutions A is used and thereaction solution B is used, a black mirror-like film was formed; in thecase of the reaction solution A being used, it was found to be ferritemade of Ni, Zn, Fe, Co and O; and in the case of the reaction solution Bbeing used, it was found to be ferrite made of Ni, Zn, Fe, and O. Anamount of Co that was contained in the ferrite film when the reactionsolution A was used was 0.03/3 by a value of Co/(Fe+Ni+Zn+Co) by molarratio. When the magnetic characteristics of the prepared ferrite filmswere measured, in both cases where the reaction solution A was used andthe reaction solution B was used, a magnetization curve in a directionin parallel with a direction of a magnetic field had a shape that was adirection of easy magnetization. Furthermore, in both cases where thereaction solution A was used and the reaction solution B was used, amagnetization curve in a direction perpendicular to a magnetic fielddepicted a hysteresis loop in a direction of hard magnetization, thatis, it was a uniaxial anisotropy ferrite film that has a direction ofeasy magnetization in a particular direction. However, the film thatused the reaction solution A was remarkable in the difference of shapesof the hysteresis loops in a direction of hard magnetization and in adirection of easy magnetization.

Each of the obtained films was measured of a real part (μ′) and animaginary part (μ″) of the magnetic permeability (in an axis of hardmagnetization) and measurements shown in Table 1 were obtained.

TABLE 1 Frequency 500 1500 20 MHz MHz MHz μ′ μ″ μ′ μ″ μ′ μ″ Reactionsolution A 120 2 85 70 20 95 Reaction solution B 80 2 35 60 10 35

Both films show excellent soft magnetic characteristics; however, onethat used the reaction solution A, having higher values of μ′ andmaintaining higher values of μ″ over a very wide frequency range,exhibited excellent characteristics.

COMPARATIVE EXAMPLE 1

For comparison purpose, with the magnets 27 removed from the apparatussuch as shown in FIGS. 2 and 3, ferrite films were formed under theconditions the same as that of example 1 according to the invention.Thereafter, it was confirmed that in both cases where the reactionsolution A was used and the reaction solution B was used, on a taken outglass substrate, a black mirror-like film was formed, and in the case ofthe reaction solution A, ferrite was made of Ni, Zn, Fe, Co and O, andin the case of the reaction solution B, ferrite was made of Ni, Zn, Feand O. When the reaction solution A was used, an amount of Co that wascontained in the ferrite film was 0.03/3 by a value of Co/(Fe+Ni+Zn+Co)by molar ratio. When the magnetic characteristics of the preparedferrite film were measured, in both cases where the reaction solution Awas and the reaction solution B was used, the magnetic characteristicswere almost isotropic magnetically in an in-plane direction.Measurements of the real part (μ′) and the imaginary part (μ″) of themagnetic permeability of the obtained films are shown in the followingTable 2.

TABLE 2 Frequency 500 1500 20 MHz MHz MHz μ′ μ″ μ′ μ″ μ′ μ″ Reactionsolution A 100 2 70 60 15 75 Reaction solution B 75 2 30 55 10 30

That is, a film in which the uniaxial anisotropy is isotropicallydispersed such as obtained in comparative example 1 or a film of whichconstituents are considered to be isotropic, in comparison with the filmsuch as obtained in embodiment 1 according to the invention in whichdirections of anisotropy of the constituents that individually have theuniaxial anisotropy are aligned in a particular direction and form afilm having the uniaxial anisotropy as a whole film, exhibits smallermagnetic permeability.

EXAMPLE 2

With reference to FIGS. 4 and 5, a glass plate rendered hydrophilic byplasma treating was disposed on tilting table 39 and was heated to 90degree centigrade with deoxygenated ion exchange water supplying.Subsequently, N₂ gas was introduced into apparatus and a deoxygenatedatmosphere was established. Reaction solutions and an oxidizing solutionsimilar to that in example 1 of the invention were prepared. After flowrates of the reaction solution and the oxidizing solution were adjustedto 30 ml/min, one of the reaction solutions A and B was supplied from anozzle for 0.5 seconds followed by removing the reaction solution owingto the fluidity imparted to the reaction solution by the gravity, andthe oxidizing solution was supplied from a nozzle for 0.5 secondsfollowed by removing the oxidizing solution owing to the fluidityimparted to the reaction solution by the gravity. With the aboveprocesses inclusive as one cycle, 2000 cycles were repeated. Thereafter,it was confirmed that in both cases where the reaction solution A wasused and the reaction solution B was used, on a taken out glasssubstrate, a black mirror-like film was formed, and in the case of thereaction solution A, ferrite was made of Ni, Zn, Fe, Co and O, and inthe case of the reaction solution B, ferrite was made of Ni, Zn, Fe andO. When the reaction solution A was used, an amount of Co that wascontained in the ferrite film was 0.03/3 by a value of Co/(Fe+Ni+Zn+Co)by molar ratio. When the magnetic characteristics of the preparedferrite films were measured, in both cases where the reaction solution Awas used and the reaction solution B was used, a magnetization curve ina direction in parallel with a direction of a magnetic field had a shapethat was a direction of easy magnetization.

Furthermore, in both cases where the reaction solution A was used andthe reaction solution B was used, a magnetization curve in a directionperpendicular to a magnetic field depicted a hysteresis loop in adirection of hard magnetization and showed to be a uniaxial anisotropyferrite film having a direction of easy magnetization in a particulardirection. However, the film that was formed by use of the reactionsolution A was conspicuous in the difference of the shapes of thehysteresis loops in a direction of hard magnetization and in a directionof easy magnetization.

The real part (μ′) and the imaginary part (μ″) of the magneticpermeability in a direction of hard magnetization of the obtained filmswere measured and results shown in the following Table 3 were obtained.

TABLE 3 Frequency 500 1500 20 MHz MHz MHz μ′ μ″ μ′ μ″ μ′ μ″ Reactionsolution A 115 2 85 70 20 90 Reaction solution B 75 2 30 55 10 35

As shown in Table 3, both films exhibit excellent soft magneticcharacteristics; however, one that was obtained by use of the reactionsolution A, being high in μ′ and also maintaining high values in μ″ overa very wide frequency range, exhibited excellent characteristics.

In the above-mentioned examples 1 and 2 according to the invention, thereaction solutions and the oxidizing solution were removed owing to thecentrifugal force or tilting of the substrate. However, as far as thereaction solution and the oxidizing solution can be uniformly removed,the fluidity imparted by supplying an inert gas or an inert gascontaining oxygen may be used.

Furthermore, in examples 1 and 2 of the invention, a magnetic field wasused as means for aligning a direction of anisotropy of constituents(grains) of the film in a particular direction; however, other meanssuch as optimization of the crystal orientation and the surfaceroughness of a material that is used for, for instance, the substratemay be used.

EXAMPLE 3

FIG. 6 shows microstrip line (MSL) 43 that is used as a substrate when aferrite thin film is formed and as a transmission line. The MSL 43 isprovided with center conductor 63 having a width of substantially 3 mmat the center portion on a surface of a 1.6 mm thick and 80 mm squareglass epoxy substrate 61 over an entire width of 80 mm and withgrounding conductor 65 on a back surface thereof, and the characteristicimpedance thereof is 50 Ω.

Furthermore, on a front surface of the MSL 43, over a substantiallyentire surface, ferrite thin film 45 that was obtained by use of thereaction solution B in example 1 of the invention is directly formed. Adirection of an axis of easy magnetization of the ferrite thin film 45is matched in a direction of a line of the MSL 43.

The transmission characteristics when a sample was disposed on the MSL43 were measured with both ends of the MSL 43 connected through coaxialcable 47 to network analyzer 49 and with the transmissioncharacteristics of the MSL 43 alone as a reference.

As shown in FIG. 7A, the reflection characteristics (S11), in spite ofthe ferrite thin film sample being formed with a large area, issufficiently low in its value. Accordingly, it is considered to be alevel that, even when the ferrite thin film is applied in an actualelectronic circuit, does not adversely affect on transmission signals.

Furthermore, as shown in FIG. 7B, the transmission characteristics(ΔS21) that are obtained by subtracting the transmission loss of the MSL43 itself are confirmed to exhibit large attenuation on a high frequencyside. From results shown in FIGS. 7A and 7B, it can be found that theferrite thin film according to the invention, when formed in atransmission line, is effective as an electromagnetic noise suppressorthat attenuates high frequency noise generated in an electronic device.Furthermore, the characteristics, by controlling an area, film thicknessand composition of the thin film sample, can be controlled to desiredcharacteristics.

As explained above, according to the first embodiment of the invention,when a ferrite thin film in which constituents (grains) constituting thefilm are regularly arranged is obtained and furthermore directions ofanisotropy of the constituents having the uniaxial anisotropy arealigned in a particular direction, a very homogeneous ferrite thin filmhaving as a whole film the uniaxial anisotropy in substantially parallelwith a direction of a thickness of a thin film or in substantiallyparallel with an in-plane direction of the thin film can be obtained,and still furthermore when the ferrite thin film, though containing Ni,Zn, Fe and O, further contains Co, the soft magnetic characteristics canbe improved.

Furthermore, according to the first embodiment of the invention, when amethod of manufacturing a ferrite film is allowed to include bringing areaction solution containing at least ferrous ion into contact with asubstrate; bringing an oxidizing solution containing at least an oxidantinto contact with the substrate; removing a residue that does notcontribute to the formation of the ferrite film of the reaction solutionand the oxidizing solution from the substrate; and furthermore bringinga reaction solution and an oxidizing solution into contact with asurface of the substrate in the presence of a magnetic field, aformation rate of the ferrite film is improved and thereby industrialproductivity is increased, and an extremely homogeneous ferrite thinfilm that has the constituents (grains or constituents analogous tothat) constituting the film regularly arranged and the uniaxialanisotropy can be obtained. Accordingly, the above manufacturing methodis large in the industrial use value.

Still furthermore, when a ferrite plating film according to the firstembodiment according to the invention is formed alone or on a support,alternatively when it is directly formed at least on one surface of anelectronic wiring board or a semiconductor integrated wafer, anelectromagnetic noise suppressor can be obtained.

Second Embodiment

First, a technical outline of another ferrite film according to thepresent invention will be briefly explained.

The present inventors, after variously studying, found that when acrystal orientation constituting a ferrite film is controlled, a ferritefilm in which a ratio of peak intensities corresponding to a (222)crystal lattice plane and a (311) crystal lattice plane in the X-raydiffraction pattern of a surface of the film, I₂₂₂/I₃₁₁, is 0.05 or morecan be obtained.

In the ferrite film, in order to obtain higher magnetic permeability,the ratio of peak intensities, I₂₂₂/I₃₁₁, is preferably made as large aspossible. The reason for higher magnetic permeability being obtainedwhen the ratio of peak intensities, I₂₂₂/I₃₁₁, is larger than 0.05 isconsidered to be related with that, when the ratio is less than 0.05,owing to the disorder of the crystal orientation of the ferrite film,potential that the individual grains intrinsically have cannot besufficiently extracted as a whole film, or the homogeneity of the filmis deteriorated or stress remains inside of the film.

Furthermore, it was found that in the ferrite film, at least one kind ofNi, Fe, Zn and O is contained. It is assumed that when one kind or moreof these elements are deficient, an ion layout in a spinel lattice islargely affected, resulting in incapability of obtaining high magneticpermeability.

Furthermore, when such a ferrite film is manufactured, a ferrite filmmay be formed on a surface of a substrate having the center line averageroughness Ra of larger than 0 and 10 μm or less according to the ferriteplating method. At this time, it was found that the ferrite film couldbe formed so that a ratio of peak intensities corresponding to the (222)crystal lattice plane and the (311) crystal lattice plane in the X-raydiffraction pattern of a surface of the film, I₂₂₂/I₃₁₁, might be largerthan 0.05 and at least one kind of Ni, Zn, Fe and O might be contained.In the ferrite film, in order to obtain higher magnetic permeability,the center line average roughness Ra is preferably made as small aspossible.

In addition, it was found that when according to the ferrite platingprocess, bringing a reaction solution containing at least ferrous ioninto contact with a substrate; bringing an oxidizing solution containingat least an oxidant into contact with a substrate; and removing residuethat does not contribute to the formation of a ferrite film of thereaction solution and the oxidizing solution from the substrate wererepeated, and the reaction solution and the oxidizing solution werebrought into contact with a surface of the substrate in the presence ofa magnetic field, the film could be improved in the formation ratethereof and thereby could be industrially mass-produced. Furthermore itwas also found that even in the case where after the crystal orientationwas controlled according to the above-mentioned process, a homogeneousfilm could be obtained with difficulty, when a surface of the substratewas plasma treated in advance, a homogeneous film more controlled in thecrystal orientation could be obtained.

In the method of manufacturing a ferrite film like this, the reason forthe center line average roughness Ra being provided to be 10 μm or lessis in that when the center line average roughness Ra is larger than 10μm, the magnetic permeability is largely deteriorated. The reason forthis is inferred to be in that a ratio of peak intensities correspondingto the (222) crystal lattice plane and the (311) crystal lattice planein the X-ray diffraction pattern of a surface of the ferrite film,I₂₂₂/I₃₁₁, becomes less than 0.05. Furthermore, the reason for thecenter line average roughness Ra being provided to be larger than 0 isbecause in order to obtain higher magnetic permeability the center lineaverage roughness Ra is preferably made as small as possible, andbecause even when the center line average roughness Ra is remarkablysmall and sufficient adherence and homogeneity cannot be obtainedwithout applying the surface treatment, the plasma treatment of asurface of the substrate enables to obtain a desired film.

An effect of previously applying plasma treatment on a surface of asubstrate is present in that by forming an oxygen-containing layer on asurface of the substrate Fe²⁺ absorption can be accelerated. The plasmatreatment of the surface of the substrate is not a necessary conditionfor manufacturing the above-mentioned homogeneous film. However, thereare cases where sufficient adherence and homogeneity cannot be obtainedwithout treatment; that is, for instance, when the center line averageroughness Ra of the surface of the substrate is extremely small, orthere is no sufficient oxygen-containing surface layer that allows Fe²⁺being uniformly absorbed on a surface of the substrate. In these cases,application of the plasma treatment allows to eliminate theseinconveniences. As the plasma for use in plasma treatment, as a type ofdischarge, glow discharge, corona discharge, boxer charger and so on canbe used. As a plasma gas, one kind or more of non-oxidizing gases suchas nitrogen, argon, helium, ammonia, and carbon tetrafluoride can beused; and as an oxygen-containing gas, one kind or two kinds or more ofoxygen, carbon dioxide, carbon monoxide, nitrogen dioxide, sulfurdioxide, and air can be used. In the case of the non-oxidizing gas beingused as a plasma gas, when a solid surface thereon free radicals aregenerated by the plasma treatment is exposed to air, on a surface of thesubstrate, an oxygen-containing surface layer can be formed.

The reason why the step of removing residue that does not contribute tothe formation of the ferrite film of the reaction solution and theoxidizing solution that is introduced in the ferrite plating processimproves a formation rate of the film and enables to form a homogeneousfilm is not clearly understood; however, it can be inferred that thesesteps suppress ferrite fine particles from being secondarily formedother than on a solid surface, in addition, have a function of allowingFe²⁺ to be uniformly absorbed on a solid surface.

Furthermore, according to the method of manufacturing the ferrite filmaccording to the invention, basically, a step in which one solution of areaction solution and an oxidizing solution is supplied followed byremoving the supplied solution and the other solution is suppliedfollowed by removing the supplied solution is repeated; however, otherthan this, a step in which two solutions are supplied simultaneouslyfollowed by removing may be repeated.

According to the second embodiment, when the crystal orientationconstituting the ferrite film is controlled, a ferrite film in which aratio of peak intensities corresponding to the (222) crystal latticeplane and the (311) crystal lattice plane in the X-ray diffractionpattern of a surface of the film, I₂₂₂/I₃₁₁, is 0.05 or more can beobtained.

In the following, several ferrite films involving the second embodimentof the invention will be specifically explained including manufacturingmethods thereof.

EXAMPLE 4

With reference to FIG. 8, ferrite film formation apparatus 51 isconstituted with two substrates 25, 25 on which a ferrite film is formeddisposed on a rotary table 23 and with tip ends of nozzles 31 and 29attached to tanks 33 and 35 that reserve solutions necessary for theplating disposed in proximity to the neighborhood of the substrates 25,25. The solutions that are reserved in the tanks 33 and 35, in order toefficiently carry out a step of removing the residue that does notcontribute to the generation of a ferrite film of the reaction solutionand the oxidizing solution that are introduced in the ferrite platingprocess, are divided in two. When a ferrite film is being manufactured,the necessary solution is well prepared by dividing into severalportions.

In the case of this ferrite film formation apparatus, when solutionsfrom severally divided reaction solution and oxidizing solution reservedin tanks 33 and 35 are supplied through the nozzles 31 and 29 to therespective substrates 25, 25, a process in which, after the solutionsupplied through, for instance, the nozzle 29 to the substrate 25 isremoved by a centrifugal force due to the rotation of the rotary table23, the solution supplied through the nozzle 31 to the substrate 25 issimilarly removed by a centrifugal force due to the rotation of therotary table 23 is repeated. In the above, two different kinds ofsolutions are supplied from the tanks 33 and 35 through two channels ofnozzles 31 and 29 to two substrates 25, 25. Instead, the apparatus maybe constituted so that different three or more kinds of solutions may besupplied from three or more tanks through three or more channels ofnozzles to three or more substrates 25, 25. Furthermore, in the aboveexplanation, a process in which one of the reaction solution and theoxidizing solution is supplied followed by removing the suppliedsolution and the other solution is supplied followed by removing thesupplied solution is repeated. Instead, a process in which two solutionsare simultaneously supplied followed by removing may be repeated. Stillfurthermore, in the above explanation, by making use of the centrifugalforce, the reaction solution and the oxidizing solution are removed fromthe substrate 25. Instead, the respective solutions may be removed byuse of the fluidity imparted to the reaction solution and the oxidizingsolution through the gravity.

In the ferrite film formation apparatus having a basic configurationlike this, first, on the rotary table 23, as several different kinds ofsubstrates 25, 25, a glass epoxy substrate A having the center lineaverage roughness Ra of substantially 15 μm, a glass epoxy substrate Bhaving the center line average roughness Ra of substantially 1 μm and aglass substrate C that is rendered hydrophilic by the plasma treatmentand has the center line average roughness Ra of less than 0.1 μm aredisposed, and under rotation at the number of revolution of 150 rpm andwith deoxygenated ion exchange water supplying, heated up to 90 degreecentigrade.

Subsequently, N₂ gas is introduced in the ferrite film formationapparatus and thereby a deoxygenated atmosphere is established.Thereafter, as the reaction solution, a solution in which FeCl₂.4H₂O,NiCl₂.6H₂O and ZnCl₂, respectively, are dissolved by 3.3, 1.3, and 0.03g/L in deoxygenated ion exchange water is prepared; an oxidizingsolution in which NaNO₂ and CH₃COONH₄, respectively, are dissolved by0.3 and 5.0 g/L in deoxygenated ion exchange water is prepared; and,from tanks 33 and 35 in which the reaction solution and the oxidizingsolution that are necessary for the plating are reserved, through thenozzles 29 and 31, the respective solutions are supplied at a flow rateof 30 ml/min for substantially 180 minutes to form a film. In theprocessing here, a reaction solution contact step, a reaction solutionremoval step, an oxidizing solution contact step and an oxidizingsolution removal step according to the above ferrite plating process arerepeated; however, as needs arise, the reaction solution in the reactionsolution contact step and the oxidizing solution in the oxidizingsolution contact step may be brought into contact with a surface of thesubstrate 25 in the presence of a magnetic field.

Thereafter, it was confirmed that a black film was formed on each oftaken out substrates and the film was made of a ferrite film involvingone of various kinds of samples made of Ni, Zn, Fe and O. As a result oftexture observation with a scanning electron microscope (SEM), it wasconfirmed that a texture having a uniform film thickness was formed.

The magnetic permeability (real part μ′ and imaginary part μ″) of theseferrite films involving the respective obtained samples were measuredand results shown in Table 4 were obtained.

TABLE 4 Surface Frequency = Frequency = Frequency = roughness 20 MHz 500MHz 1500 MHz (μm) μ′ μ″ μ′ μ″ μ′ μ″ Substrate A 15 20 2 20 2 15 10Substrate B 1 45 2 20 35 15 30 Substrate C <0.1 60 2 20 50 5 30

From Table 4, it is found that ferrite films formed on the glass epoxysubstrate B (referred to simply as “substrate B”) and the glasssubstrate C (referred to simply as “substrate C”) exhibit excellent softmagnetic characteristics; however, in the case of a ferrite film formedon the glass epoxy substrate A (referred to simply as “substrate A”),both the real part μ′ in a relatively low frequency (20 MHz) and theimaginary part in a relatively high frequency (500 MHz and 1500 MHz) arelow, that is, the soft magnetic characteristics are remarkablydeteriorated. Accordingly, the ferrite films formed on the substrates Band C that are excellent in the soft magnetic characteristics in thehigh frequency region are target samples involving embodiments of thepresent invention.

Furthermore, Cu Kα X-ray diffraction patterns of surfaces of the ferritefilms involving the respective obtained samples were evaluated andresults shown in Table 5 were obtained.

TABLE 5 Surface roughness Peak intensity ratio Ra (μm) I₂₂₂/I₃₁₁Substrate A 15 0.05 Substrate B 1 0.07 Substrate C <0.1 10

From Table 5, it is found that there is a tendency in that a ratio ofpeak intensities corresponding to a crystal lattice plane (222) and acrystal lattice plane (311), I₂₂₂/I₃₁₁, becomes smaller in its value asthe center line average roughness Ra (referred to simply as “surfaceroughness Ra”) of the substrate becomes larger. Accordingly, the ferritefilms formed on the substrates B and C of which peak intensity ratiosI₂₂₂/I₃₁₁ exceed 0.05 are target samples involving embodiments of thepresent invention.

COMPARATIVE EXAMPLE 2

Now, as comparative example 2, in the ferrite film formation apparatus51 as shown in FIG. 8, similarly, first, on a rotary table 23, as asubstrate 25, a glass substrate D that is not rendered hydrophilic bythe plasma treatment and has the center line average roughness Ra ofless than 0.1 μm was disposed, and a film was formed under the sameconditions as in the above embodiment. Thereafter, it was confirmed thaton a taken out substrate a black film was formed and the black film wasa ferrite film made of Ni, Zn, Fe and O. However, according to resultsof the texture observation by use of a scanning electron microscope(SEM), it was confirmed that, in addition to the ferrite film on theglass substrate D being uneven in the film thickness in comparison withthat on the glass substrate C obtained according to embodiment 1, thetexture homogeneity was extremely deteriorated.

Also with the ferrite film involving the sample obtained here, magneticpermeability (real part μ′ and imaginary part μ″) at predetermined highfrequencies (20 MHz, 500 MHz and 1500 MHz) was measured and comparedwith that of the ferrite film formed on the glass substrate C obtainedaccording to the previous embodiment, results shown in the followingTable 6 were obtained.

TABLE 6 Frequency = Frequency = Frequency = Plasma Surface 20 MHz 500MHz 1500 MHz treatment roughness (μm) μ′ μ″ μ′ μ″ μ′ μ″ Substrate C Yes<0.1 60 2 20 50 5 30 Substrate D No <0.1 20 2 20 3 15 10

From table 6, it is found that the ferrite film formed on the glasssubstrate D (referred to simply as “substrate D”) is low both in thereal part μ′ in a relatively low frequency (20 MHz) and the imaginarypart μ″ in relatively high frequencies (500 MHz and 1500 MHz), that is,the soft magnetic characteristics are remarkably deteriorated.

COMPARATIVE EXAMPLE 3

In the next place, as comparative example 3, with the ferrite filmformation apparatus 51 such as shown in FIG. 8, similarly, first, on arotary table 23, as a substrate 25 a glass substrate C renderedhydrophilic by the plasma treatment and having the center line averageroughness Ra of less than 0.1 μm was disposed; and, under the conditionsthe same as that of the above-mentioned embodiment except for a solutionin which FeCl₂.4H₂O and ZnCl₂, respectively, are dissolved by 3.3 and0.03 g/L in deoxygenated ion exchange water being used as the reactionsolution, a film was formed. Thereafter, it was confirmed that on ataken out substrate a black film was formed and the black film was aferrite film made of Zn, Fe and O. Furthermore, also according toresults of the texture observation by use of a scanning electronmicroscope (SEM), it was confirmed that a texture homogeneous in thefilm thickness was obtained. However, when the magnetic permeability(real part μ′ and imaginary part μ″) was measured of the obtainedferrite film in the high frequency zone, it was found that the magneticpermeability was substantially 1. Here, whether the reaction solutioncontains NiCl₂.6H₂O as in the previous embodiment or not is a point. Asa result, it is shown that the difference of the composition of thereaction solution largely affects on the soft magnetic characteristicsof the ferrite films that are formed.

COMPARATIVE EXAMPLE 4

Furthermore, as separate comparative example 4, with the ferrite filmformation apparatus 51 such as shown in FIG. 8, similarly, first, on therotary table 23, as the substrate 25, a glass substrate C that isrendered hydrophilic by the plasma treatment and has the center lineaverage roughness Ra of less than 0.1 μm was disposed, and a film wasformed under the same conditions as in the above embodiment except forthe number of revolutions of the rotary table 23 being set at 20 rpm.Thereafter, it was confirmed that on a taken out substrate a ferritefilm was formed; however, according to results of the textureobservation by use of a scanning electron microscope (SEM), it wasconfirmed that, in addition to a film thickness being very uneven, thehomogeneity of the texture was very much deteriorated.

Also with the ferrite film involving the sample obtained here, themagnetic permeability (real part μ′ and imaginary part μ″) atpredetermined high frequencies (20 MHz, 500 MHz and 1500 MHz) wasmeasured and compared with that of the ferrite film formed on the glasssubstrate C obtained according to the previous embodiment, and resultsshown in the following Table 7 were obtained.

TABLE 7 Frequency = Frequency = Frequency = Number of Surface 20 MHz 500MHz 1500 MHz revolutions (rpm) roughness (μm) μ′ μ″ μ′ μ″ μ′ μ″Substrate C 150 <0.1 60 2 20 50 5 30 Substrate C 20 <0.1 10 2 10 2 10 2

From table 7, it is found that although the rotation function of therotary table 23 of the ferrite film formation apparatus shown in FIG. 8has an operation of applying a centrifugal force on the surface of thesubstrate, in the case of the glass substrate C of which number ofrevolutions is relatively small (number of revolutions: 20 rpm), incomparison with the glass substrate C according to the previousembodiment where the number of revolutions is relatively large (numberof revolutions: 150 rpm), the magnetic permeability (real part μ′ andimaginary part μ″) was remarkably deteriorated in the high frequencyzone. Accordingly, the present result shows that, when the ferriteplating process is introduced to form a ferrite film, that is, when thesteps of bringing the reaction solution containing at least ferrous ioninto contact with the substrate, of bringing the oxidizing solutioncontaining at least an oxidant into contact with the substrate and ofremoving the residue that does not contribute to the formation of theferrite film of the reaction solution and the oxidizing solution fromthe substrate are repeated to form the ferrite film, the application ofthe centrifugal force larger than a predetermined value is indispensablefor efficiently mass-producing the ferrite films having excellenttexture with an increased formation rate of the films.

As mentioned above, according to the second embodiment of the invention,when a ferrite film is formed on a surface of a substrate having thecenter line average roughness Ra of 0 or more and 10 μm or lessaccording to the ferrite plating process, on the basis where the ferritefilm is formed so that a ratio of peak intensities corresponding to a(222) crystal lattice plane and a (311) crystal lattice plane in theX-ray diffraction pattern of a surface of the substrate, I₂₂₂/I₃₁₁, maybe larger than 0.05 and at least one kind of Ni, Zn, Fe and O may becontained, in addition to the above, according to the ferrite platingprocess, the step of bringing the reaction solution containing at leastferrous ion into contact with the substrate, the step of bringing theoxidizing solution containing at least an oxidant into contact with thesubstrate and the step of removing the residue that does not contributeto the formation of the ferrite film of the reaction solution and theoxidizing solution from the substrate are repeated. Accordingly, thehomogeneous ferrite film that is controlled in the crystal orientationand has high magnetic permeability can be mass-produced with an improvedformation rate, resulting in being industrially very advantageous.

Third Embodiment

Subsequently, still another invention will be specifically explained.

In the present invention, a ferrite thin film in which constituents thatconstitutes a ferrite film, for instance, grains or constituentsanalogous to that, are regularly arranged is obtained; furthermore anextremely homogeneous ferrite film of which constituents have theuniaxial anisotropy or multiaxial anisotropy and that is, as a wholefilm, in an in-plane direction of the thin film, magnetically isotropiccan be obtained; and although the ferrite thin film contains Ni, Zn, Feand O, when Co is further contained, the soft magnetic characteristicscan be improved.

As to an amount of Co that is contained in the ferrite film according tothe invention, by a molar ratio, a value of Co/(Fe+Ni+Zn+Co) is 0/3 ormore and 0.3/3 or less, and most preferably substantially from 0.01/3 to0.1/3.

In another mode of the invention, the step of removing the reactionsolution and the oxidizing solution allows improving the formation rateof the ferrite plating film and forming homogeneous columnar grains;however, the details thereof are not clarified. However, it isconsidered that the step of removing the reaction solution and theoxidizing solution suppresses ferrite fine grains from being secondarilyformed other than on the solid surface and allows Fe²⁺ to behomogeneously absorbed on the solid surface.

As mentioned above, for instance, the literatures 7 and 8 disclose amethod of improving the soft magnetic characteristics by applying theferrite plating in a magnetic field; in particular, the literature 8describes that when the ferrite plating is applied in a magnetic field,a film having the uniaxial anisotropy can be obtained.

In embodiments according to the literatures 7 and 8, there is adescription that “a plating solution may be separately supplied”;however, all embodiments in the literatures adopt a method in which aplurality of plating solutions is mixed before the ferritecrystallization and supplied to a substrate. Accordingly, it is inferredthat because ferrite fine grains that are secondarily formed other thanon a solid surface disturb the crystal growth and Fe²⁺ is unevenlyabsorbed on a solid surface, a ferrite film that is an aggregation ofhomogeneous grains may be obtained with difficulty. Furthermore, since adirection of an applied magnetic field is directed in one direction, itis different from still another mode of the invention.

According to, for instance, the literature 9, there is a descriptionthat excellent magnetic characteristics can be obtained when a weightratio of Co/Fe in the film is in the range of from 0.001 to 0.3.However, since the usage is for magnetic recording media, the inventionof the literature 9 intends to obtain higher coercive force and higherresidual magnetic flux density; that is, the literature 9 is clearlydifferent from still another mode of the present invention in the usageand the directionality.

Furthermore, according to, for instance, the literature 6, a process isproposed in which a step where a reaction solution containing at leastferrous ion is brought into contact with the substrate followed bybringing an oxidizing solution containing at least an oxidant intocontact with the substrate is repeated, and thereby a ferrite film isformed on a surface of the substrate; and it is said that thereby theformation rate of the ferrite film can be improved. However, in theliterature 6, the step of removing the reaction solution containing atleast ferrous ion and the oxidizing solution containing at least anoxidant is not clearly described.

According to the study of the present inventors, the step of removingthe reaction solution containing at least ferrous ion and the solutioncontaining at least an oxidant is very important and indispensable inimproving the formation rate of the ferrite plating film and in forminghomogeneous grains.

Furthermore, because the ferrite plating film according to the inventionhas excellent magnetic loss characteristics in a high frequency region,the ferrite plating film, when formed singly or on a support, can beused as an electromagnetic noise suppressor; and furthermore, when theferrite plating film is formed directly at least on one surface of anelectronic wiring board or a semiconductor integrated wafer, anelectronic wiring board or a semiconductor integrated wafer concurrentlyworking as an electromagnetic noise suppressor can be realized.

In the next place, a third embodiment according to the invention will beexplained.

With reference to FIGS. 9 and 10, in plating apparatus, on rotary table23, substrates 25 thereon a ferrite film is formed are disposed. On bothsides of the rotary table 23, magnets 55 are disposed and play the roleof applying a magnetic field to the substrates 25. Furthermore, themagnets 55 are fixed on magnet supporting tables 57 independently fromthe rotary table 23 and independently from the revolution of the rotarytable 23 a magnetic field is applied in one direction. Above thesubstrates 25, in order to supply plating solutions reserved in tanks 35and 33, respectively, to the substrates 25, nozzles 29 and 31 connectedto the tanks 33 and 35 are respectively disposed.

In order to efficiently remove the reaction solution and the oxidizingsolution in the plating step, necessary solutions may be well preparedby dividing into several portions. Furthermore, in FIGS. 9 and 10, acase where a solution necessary for the plating is divided into two isshown.

Solutions reserved in the tanks 33 and 35 are supplied through thenozzles 29 and 31 to the substrates 25. At that time, a step in whichafter the solution is supplied through, for instance, the nozzle 31 tothe substrate 25, the supplied solution is removed by a centrifugalforce due to revolution, and the solution supplied through the nozzle 29to the substrate 25 is removed by the centrifugal force due torevolution is repeated.

For comparison purpose, an example that uses the apparatus shown inFIGS. 4 and 5 that were used in the first embodiment will be explained.

With reference to FIGS. 2 and 3, on rotary table 23, substrates 25thereon a ferrite film is formed are disposed. Also magnets 55 aredisposed on the rotary table 23, revolve together with the substrates 25and play the role of applying a magnetic field to the substrates 25. Themagnetic field that is applied on the substrates 25 is adjusted so as tobe the same as that in FIG. 9.

With reference to FIG. 11, plating apparatus according to still anotherexample according to the third embodiment of the invention uses, whenthe reaction solution and the oxidizing solution are removed from thesubstrate, the fluidity imparted to the reaction solution and theoxidizing solution due to the gravity. Also in the apparatus, similarlyto FIG. 9, solutions reserved in tanks 33 and 35 are supplied throughnozzles 29 and 31, respectively, to substrates 25 disposed on tiltingtable 39. At this time, a step in which after the solution is suppliedthrough, for instance, the nozzle 29 to the substrate 25, the suppliedsolution is removed by the fluidity imparted to the solution due to thegravity, and after the solution is supplied through nozzle 29 to thesubstrate 25, the supplied solution is removed by the fluidity impartedto the solution due to the gravity is repeated.

Furthermore, in the invention, an example is shown in which a step inwhich after one solution is supplied, the supplied solution is removed,and after the other solution is supplied, the supplied solution isremoved is repeated; however, two solutions may be simultaneouslysupplied.

In the following, a specific example of preparation of a ferrite thinfilm according to the third embodiment of the invention will beexplained.

EXAMPLE 5

On rotary table 9 such as shown in FIGS. 9 and 10, as substrates 25,glass plates rendered hydrophilic by plasma treatment are disposed andheated to 90 degree centigrade while rotating at 150 rpm under supply ofdeoxygenated ion exchange water. In the next place, in the apparatus, N₂gas was introduced and a deoxygenated atmosphere was established. Twokinds of reaction solutions were prepared. Into deoxygenated ionexchange water, FeCl₂.4H₂O, NiCl₂.6H₂O, ZnCl₂, and CoCl₂.6H₂O,respectively, were dissolved by 3.3, 1.3, 0.03, and 0.1 g/L, and therebya solution A was prepared. Into deoxygenated ion exchange water,FeCl₂.4H₂O, NiCl₂.6H₂O, and ZnCl₂, respectively, were dissolved by 3.3,1.3, and 0.03 g/L, and thereby a solution B was prepared. Any one of thereaction solutions A and B and an oxidizing solution in which indeoxygenated ion exchange water, NaNO₂ and CH₃COONH₄, respectively, weredissolved by 0.3 and 5.0 g/L were respectively supplied from the nozzlesat a flow rate of 30 ml/min for substantially 30 minutes. In theapparatus, since on a surface of the substrate, a magnetic field ofsubstantially 50 Oe was applied substantially in parallel with a filmsurface and the magnets are fixed independently from the rotary table,the substrate is considered to obtain the substantially the same effectas that in the case where the substrate is disposed in a rotatingmagnetic field. Thereafter, it was confirmed that on a taken out glasssubstrate, in all cases where the reaction solution A was used and thereaction solution B was used, a black mirror-like film was formed; inthe case of the reaction solution A being used, it was ferrite made ofNi, Zn, Fe, Co and O; and in the case of the reaction solution B beingused, it was ferrite made of Ni, Zn, Fe, and O. An amount of Co that wascontained in the ferrite film when the reaction solution A was used was0.03/3 by a value of molar ratio of Co/(Fe+Ni+Zn+Co). When amagnetization curve of the prepared ferrite film was measured, in bothcases of the reaction solution A being used and the reaction solution Bbeing used, magnetization curves in any directions in a film plane hadsubstantially the same shape, that is, a ferrite film magneticallyisotropic in in-plane directions of the thin film was obtained. Each ofobtained films was measured of a real part (μ′) and an imaginary part(μ″) of magnetic permeability and measurements shown in Table 8 wereobtained.

TABLE 8 Frequency 500 1500 20 MHz MHz MHz μ′ μ″ μ′ μ″ μ′ μ″ Reactionsolution A 100 2 70 60 15 75 Reaction solution B 75 2 30 55 10 30

Both films exhibit excellent soft magnetic characteristics; however, onethat was obtained by use of the reaction solution A, being high in μ′and maintaining high values in μ″ over a very wide frequency range,exhibited excellent characteristics.

EXAMPLE 6

With the magnets removed from the apparatus such as shown in FIGS. 9 and10, under the conditions the same as that in the example 5 of theinvention, films were prepared. According to measurement of themagnetization curve of the prepared ferrite film, in both cases of thereaction solutions A and B, in all directions in a film plane, themagnetization curves had substantially the same shapes; that is, aferrite thin film magnetically isotropic in in-plane directions of thethin film was obtained. The real part (μ′) and the imaginary part (μ″)of the magnetic permeability of the obtained films are shown in thefollowing Table 9.

TABLE 9 Frequency 20 500 1500 MHz MHz MHz μ′ μ″ μ′ μ″ μ′ μ″ Reactionsolution A 95 2 75 55 15 75 Reaction solution B 75 2 30 50 10 30

Both films exhibit excellent soft magnetic characteristics; however, onethat was obtained by use of the reaction solution A, being high in μ′and maintaining high values of μ″ over a very wide frequency range,exhibited excellent characteristics.

EXAMPLE 7

On tilting table 39 of the apparatus such as shown in FIG. 11, assubstrate 25, a glass plate rendered hydrophilic by the plasma treatmentwas disposed and heated to 90 degree centigrade under supply ofdeoxygenated ion exchange water. Subsequently, N₂ gas was introducedinto the apparatus and thereby a deoxygenated atmosphere was establishedtherein. Reaction solutions and an oxidizing solution were preparedsimilarly to that according to example 5 of the invention. The flowrates of the reaction solution and the oxidizing solution were adjustedto 30 ml/min. Thereafter, with a step in which one of the reactionsolutions A and B was supplied from a nozzle for 0.5 seconds, thereafterthe reaction solution was removed owing to the fluidity imparted to thereaction solution by the gravity, and after the oxidizing solution wassupplied from a nozzle for 0.5 seconds, the oxidizing solution wasremoved owing to the fluidity imparted to the reaction solution by thegravity as one cycle, 2000 cycles were repeated. Thereafter, it wasconfirmed that on a taken out glass substrate, in all cases of thereaction solutions A being used and the reaction solution B being used,a black mirror-like film was formed; in the case of the reactionsolution A being used, it was ferrite made of Ni, Zn, Fe, Co and O; andin the case of the reaction solution B being used, it was ferrite madeof Ni, Zn, Fe, and O. An amount of Co that was contained in the ferritefilm when the reaction solution A was used was 0.03/3 by a value ofmolar ratio of Co/(Fe+Ni+Zn+Co). When a magnetization curve of theprepared ferrite film was measured, in both cases of the reactionsolution A and the reaction solution B, the magnetization curves in alldirections in a film plane had substantially the same shape, that is, aferrite film magnetically isotropic in in-plane directions of the thinfilm was obtained. Each of obtained films was measured of a real part(μ′) and an imaginary part (μ″) of the magnetic permeability andmeasurements shown in Table 10 were obtained.

TABLE 10 Frequency 500 1500 20 MHz MHz MHz μ′ μ″ μ′ μ″ μ′ μ″ Reactionsolution A 100 2 70 65 15 80 Reaction solution B 75 2 30 55 10 35

Both films exhibit excellent soft magnetic characteristics; however, onethat was obtained by use of the reaction solution A, being high in μ′and maintaining high values in μ″ over a very wide frequency range,exhibited excellent characteristics. In the embodiments according to theinvention, the reaction solution and the oxidizing solution were removedowing to the centrifugal force or the tilting of the substrate; however,as far as the reaction solution and the oxidizing solution can beuniformly removed, the fluidity that can be imparted by supply of aninert gas or an inert gas containing oxygen may be used.

Furthermore, in example 5 of the invention, as means for randomizing adirection of the anisotropy of the constituents (grains) of the film, arotating magnetic field was used; however, other means such asoptimization of the crystal orientation and the surface roughness of amaterial that is used for the substrate may be used.

EXAMPLE 8

The suppression effect of electromagnetic noise of the ferrite filmsobtained according to the invention, similarly to the first embodiment,was confirmed by use of an evaluation system shown in FIG. 6. Withreference to FIG. 6, microstrip line (MSL) 43 is used as a substratewhen a ferrite thin film is formed and a transmission line. The MSL 43is provided with center conductor 63 having a width of substantially 3mm in the center portion of a surface of 1.6 mm thick and 80 mm squareglass epoxy substrate 61 over an entire width of 80 mm, a back surfacethereof forms grounding conductor 65 and the characteristic impedancethereof is 50 Ω. Furthermore, on a front surface of the MSL43, over asubstantially entire surface, ferrite thin film 45 obtained by use ofthe reaction solution B in example 5 of the invention is directlyformed.

The transmission characteristics when a sample was disposed on the MSL43 were measured with both ends of the MSL 43 connected through coaxialcables 47 to network analyzer 49 and with the transmissioncharacteristics of the MSL 43 alone as a reference.

With reference to FIG. 12A, the reflection characteristics (S11), inspite of the ferrite thin film sample being formed with a large area, issufficiently low in its value. Accordingly, it is considered to be alevel that, even when the ferrite thin film is applied in, for instance,an actual electronic circuit, does not adversely affect on transmissionsignals.

As shown in FIG. 12B, in the transmission characteristics (ΔS21) thatare obtained by subtracting the transmission loss of the MSL 43 itself,a large attenuation on a high frequency side can be confirmed. Fromthese results, it can be found that the ferrite thin film according tothe invention, when formed in a transmission line, is effective as anelectromagnetic noise suppressor that can attenuate high frequency noisegenerated in an electronic device. Furthermore, the characteristics, bycontrolling an area, film thickness and composition of the thin filmsample, can be controlled to desired characteristics.

As explained above, according to the third embodiment of the invention,a ferrite thin film in which constituents (grains or constituentsanalogous to that) constituting the ferrite film are regularly arrangedcan be obtained, and furthermore a very homogeneous ferrite thin film inwhich the constituents have the uniaxial anisotropy or multiaxialanisotropy and as a whole film in in-plane directions of the thin filmthe magnetic characteristics are isotropic can be obtained.

Furthermore, according to the third embodiment of the invention, when astep of bringing a reaction solution containing at least ferrous ioninto contact with a substrate; a step of bringing an oxidizing solutioncontaining at least an oxidant into contact with the substrate; and astep of removing a residue that does not contribute to the formation ofthe ferrite film of the reaction solution and the oxidizing solutionfrom the substrate are provided, a manufacturing method of ferrite filmsthat allows improving the formation rate and increasing the industrialproductivity, regularly arranging the constituents that constitute thefilm and thereby obtaining very homogeneous ferrite film magneticallyisotropic in a film plane can be obtained; accordingly, the industrialuse value is very large.

Furthermore, when a ferrite plating film according to the thirdembodiment according to the invention is formed alone or formed on asupport, alternatively when it is directly formed at least on onesurface of an electronic wiring board or a semiconductor integratedwafer, an electromagnetic noise suppressor can be obtained.

1. A method of manufacturing a ferrite film the method includes thesteps of: bringing a reaction solution containing at least a ferrous ioninto contact with a substrate; removing the reaction solution from thesubstrate; bringing an oxidizing solution containing at least an oxidantinto contact with the substrate; and removing residue that does notcontribute to the formation of the ferrite film of the reaction solutionand the oxidizing solution from the substrate, wherein the ferrite filmhas magnetic anisotropy or is magnetically isotropic; has a ratio ofpeak in intensities corresponding to a (222) crystal lattice plane and a(311) crystal lattice plane in an x-ray diffraction pattern of a surfaceof the film and is represented by I₂₂₂/I₃₁₁, said ratio being largerthan 0.05; is composed of at least one of Ni, Zn, Fe, and O and containsCo in a molar ratio of Co/(Fe+Ni+Zn+Co) of 0.01/3 to 0.3/3.
 2. A methodof manufacturing a ferrite film as set forth in claim 1, wherein theremoving the reaction solution and the oxidizing solution from thesubstrate makes use of the fluidity imparted to the reaction solutionand the oxidizing solution due to gravity and a centrifugal force.
 3. Amethod of manufacturing a ferrite film as set forth in claim 1, whereinthe ferrite film is formed by repeating the above-mentioned respectivesteps.
 4. A method of manufacturing a ferrite film as set forth in claim1, wherein as the substrate, use is made of a substrate having thecenter line average roughness Ra of larger than 0 and 10 μm or less. 5.A method of manufacturing a ferrite film, the method including the stepsof: bringing a reaction solution containing at least a ferrous ion intocontact with a substrate; removing the reaction solution from thesubstrate; bringing an oxidizing solution containing at least an oxidantinto contact with the substrate; and removing residue that does notcontribute to the formation of the ferrite film of the reaction solutionand the oxidizing solution from the substrate; wherein the ferrite filmhas magnetic anisotropy or is magnetically isotropic; has a ratio ofpeak in intensities corresponding to a (222) crystal lattice plane and a(311) crystal lattice plane in an X-ray diffraction pattern of a surfaceof the film and is represented by I₂₂₂/I_(311,) said ratio being largerthan 0.05; is composed of at least one of Ni, Zn, Fe, and O.
 6. A methodof manufacturing a ferrite film as set forth in claim 5, wherein theremoving the reaction solution and the oxidizing solution from thesubstrate makes use of the fluidity imparted to the reaction solutionand the oxidizing solution due to gravity and a centrifugal force.
 7. Amethod of manufacturing a ferrite film as set forth in claim 5, whereinthe ferrite film is formed by repeating the above-mentioned respectivesteps.
 8. A method of manufacturing a ferrite film as set forth in claim5, wherein as the substrate, use is made of a substrate having thecenter line average roughness Ra of larger than 0 and 10 μm or less.